The present invention relates to methods for monitoring drilling fluids and, more specifically, to systems and methods for monitoring a drilling fluid for the formation of gas hydrates.
During the drilling of a hydrocarbon-producing well, a drilling fluid or mud is continuously circulated from the surface down to the bottom of the hole being drilled and back to the surface again. The drilling fluid serves several functions, one of them being to transport wellbore cuttings up to the surface where they are separated from the drilling fluid. Another function of the drilling fluid is to provide hydrostatic pressure on the walls of the drilled borehole so as to prevent wellbore collapse and the resulting influx of gas or liquid from the formations being drilled. For several reasons, it can be important to precisely know the characteristics and chemical composition of such drilling fluids.
Typically, the analysis of drilling fluids has been conducted off-line using laboratory analyses which require the extraction of a sample of the fluid and a subsequent controlled testing procedure usually conducted at a separate location. Depending on the analysis required, however, such an approach can take hours to days to complete, and even in the best case scenario, a job will often be completed prior to the analysis being obtained. Although off-line, retrospective analyses can be satisfactory in certain cases, but they nonetheless do not allow real-time or near real-time analysis capabilities. As a result, proactive control of drilling operations cannot take place, at least without significant process disruption occurring while awaiting the results of the analysis. Off-line, retrospective analyses can also be unsatisfactory for determining true characteristics of a drilling fluid since the characteristics of the extracted sample of the drilling fluid oftentimes changes during the lag time between collection and analysis, thereby making the properties of the sample non-indicative of the true chemical composition or characteristic.
Monitoring drilling fluids in real-time can be of considerable interest in order to determine how the drilling fluid changes over time, thereby serving as a quality control measure that may be useful in drilling fluid maintenance and drilling optimization. For instance, the viscosity of the drilling fluid is an important characteristic to monitor since it contributes to the capability of the drilling fluid to adequately transport cuttings. Clays, such as bentonite clay, are often added to the drilling fluid so as to maintain the drilled cuttings suspended within the drilling fluid as they move up the borehole. The density of the drilling fluid is another significant characteristic to monitor. The density must exhibit a certain hydrostatic pressure on the formation in order to avoid wellbore collapse, but not too large such that it would fracture the formation. Weighting materials, such as barite, are often added to the drilling fluid to make it exert as much pressure as needed to contain the formation pressures. Several other chemicals or substances may be added to the drilling fluid to give the drilling fluid the exact properties it needs to make it as easy as possible to drill the wellbore.
In order to optimize the performance of a drilling fluid during drilling operations, the physical and chemical properties of the drilling fluid and its component parts must be carefully monitored and controlled. As such, there is a continued and ongoing need for improved methods and systems that provide real time monitoring of drilling fluids.